More than 2 million residents along the Eastern Seaboard have been ordered to move to safer places as Hurricane Irene lumbers toward the Mid-Atlantic region.

Residents of low-lying areas of New York City and those in the summer resort towns along the 100-mile Jersey Shore were ordered to evacuate Friday. Hurricane warnings were issued from North Carolina to New York, and watches were posted farther north, on the islands of Nantucket and Martha's Vineyard off Massachusetts. Evacuation orders covered at least 2.3 million people, including 1 million in New Jersey, 315,000 in Maryland, 300,000 in North Carolina, 200,000 in Virginia and 100,000 in Delaware.

The massive Category 2 hurricane, which is expected to make landfall in North Carolina early Saturday, slowed down slightly. The National Hurricane Center said late Friday that the storm was moving at 13 mph, down from the 14 mph it was moving earlier in the evening. But it still packs 100 mph winds and remains dangerous. Some 65 million people from the Carolinas to Massachusetts could be in Irene's path.

"Don't wait. Don't delay," said President Obama, who decided to cut short his summer vacation by a day and return to Washington, where a state of emergency has also been declared. "I cannot stress this highly enough: If you are in the projected path of this hurricane, you have to take precautions now."

"This is probably the largest number of people that have been threatened by a single hurricane in the United States," said Jay Baker, a geography professor at Florida State University.

Rain and tropical storm-force winds of at least 39 mph were already pelting the coasts of the Carolinas on Friday as Irene tracked north, snapping power lines and flooding streets. Officials warned of dangerous rip currents as Irene roiled the surf. Thousands already were without power. By Friday evening 50 mph winds were measured at Wrightsville Beach, N.C.

Experts are forecasting billions of dollars in losses, though the storm's economic impact will depend on factors including its size and speed and where it makes landfall. Computer models from catastrophic-insurance provider ICAT put the estimated damage at $4.7 billion, a figure that includes destruction of homes, cars, public infrastructure and other property caused by high winds and flooding.

Escape From New York ... And The Jersey Shore

In New York state, where Obama declared a state of emergency, Irene has already prompted several firsts: New York City Mayor Michael Bloomberg on Friday issued an unprecedented evacuation order for residents of coastal areas of Staten Island, Brooklyn and Queens, as well as the financial district in Lower Manhattan, Governor's Island, and parts of Battery Park City, Coney Island and the Rockaways. The low-lying areas, scattered across the city, are home to about 270,000 residents.

But it was not clear how residents would get out or where they would go. Most New Yorkers don't have a car. On top of that, New York City officials also said they were shutting down the city's massive subway and transit system by noon Saturday, just hours after the first rain is expected to fall.

Michael Brennan of the National Hurricane Center in Miami said the geography of the coastline makes low-lying areas of New York especially vulnerable.

"Near ... New York City is an area where a lot of water can be funneled up into a very small area if you get a big surge of easterly flow," Brennan told NPR. "So that's an area where the storm surge can be enhanced."

Trains, Planes And Automobiles

Irene is also playing havoc with planes, trains and other forms of transit along the Eastern Seaboard.

The storm could strike major airports from Washington to Boston. In anticipation, more than 2,400 flights have been canceled through Monday.

Delta Air Lines is canceling 1,300 flights and will shut down at New York City-area airports on Sunday until the hurricane passes.

JetBlue is dropping 880 flights over the weekend, mostly in New York and Boston. American Airlines scrubbed 265 flights on Saturday and probably more than that Sunday. Southwest Airlines planned to stop flights to and from Norfolk, Va., beginning Saturday morning.

The five main New York City-area airports will be closed to arriving passenger flights beginning at noon on Saturday because of Hurricane Irene. The suspension includes John F. Kennedy International and LaGuardia airports in New York City, and Newark Liberty International in New Jersey — three of the busiest airports in the nation.

Mass transit in suburban Philadelphia will halt at 12:30 a.m. Sunday. And Amtrak has suspended service south from Washington.

Gasoline stations along the East Coast began to run dry Friday, as drivers rushed for a last-minute fill-up before the storm. Utility officials say millions of people are in danger of losing electric power, some for days. Analysts don't expect widespread or long-lasting gas shortages, though, nor do they expect prices for power and gas to rise.

'We're Going To Have Damages. We Just Don't Know How Bad'

Risks are many from Irene: Surging seas, drenching rains, flash floods, high winds and protracted power outages are all possibilities the Federal Emergency Management Agency director wasn't counting out.

"We're going to have damages. We just don't know how bad," said FEMA chief Craig Fugate. "This is one of the largest populations that will be impacted by one storm at one time."

Federal officials have directed Northeast residents to ready.gov for information on how to prepare for the storm.

Homeland Security Secretary Janet Napolitano told CNN Friday afternoon, "We are reminding people today that they are part of our team — they need to prepare."

Irene comes on the heels of a magnitude 5.8 earthquake that rattled the East Coast on Tuesday. After the temblor, cellphone service was spotty at best in many affected regions, as people rushed to make calls, clogging networks. As Irene bears down on the Mid-Atlantic, "I urge people to use other forms of communication if you can," Napolitano said.